Instructions
Turn on the PlayStation 3. When the system loads, you are taken to the "PlayStation 3 Menu." Use the left analog stick to navigate to the "PlayStation Store" Menu, and press the "X" button. You are then taken to the "PlayStation Store" menu.
Use the right analog stick to scroll down to the "Add On" option, and press the "X" button to access the "Add On" menu. Select the "Search by Title" option. Type in "W" for "World at War" on the on-screen keyboard. All the games that start with "W" are displayed. Scroll through the titles until you find "World at War," and click the "X" button. You are then taken to a page displaying all the available downloads for the game. Select the map pack.
Confirm the download, and select the memory device you want the file saved to. The download begins next, so do not turn off the system. When the download finishes, restart the system. Then start your game.